Recently, a vehicle head-up display apparatus is commercialized. With the apparatus, a display image is projected to a vehicle windshield glass and forms a virtual image in front of a driver of the vehicle. As a result, the driver can visually recognize the display image without averting his/her eyes from the front while driving the vehicle.
In such a vehicle head-up display apparatus, a virtual image is displayed on a curved windshield glass, causing distortion of the virtual image. To overcome such a deficiency, Patent Literature 1 teaches a technique to reduce distortion of a virtual image by modifying optical parameters of the optical system for projecting the virtual image.